DETROIT — Faulty air bags — which have already led to the recall of millions of cars worldwide — are being blamed for a new round of recalls in the U.S.

The National Highway Traffic Safety Administration, the government’s auto safety agency, said Monday that BMW, Chrysler, Ford, Honda, Mazda, Nissan and Toyota will recall cars sold in places where hot, humid weather can potentially affect the air bags.

The older-model cars have air bag inflators that can rupture. If that happens, the air bags might not work properly in a crash, and shards from the broken system could fly out and cause injury.

They all have air bag systems made by Takata Corp., a Tokyo-based supplier of seat belts, air bags, steering wheels and other auto parts.

In letters to the government, the automakers all said they are cooperating with the recall even though they haven’t yet determined whether the air bags are a safety hazard. Dealers will replace the inflators for free and the automakers will send the inflators to Takata for further testing.

NHTSA opened an investigation this month after getting six reports of air bags rupturing in Florida and Puerto Rico. Three people were injured in those cases. It had estimated 1.1 million vehicles in the U.S. could be affected, but the total is likely to climb.

Honda, for example, said it will include 10 states and territories in its recall, including Texas, Georgia and South Carolina. Takata recommended recalling cars in four places: Florida, Hawaii, Puerto Rico and the U.S. Virgin Islands.

The government said it wanted to act quickly in warm states while it continues to investigate the issue.

“Based on the limited data available at this time, NHTSA supports efforts by automakers to address the immediate risk in areas that have consistently hot, humid conditions over extended periods of time,” the agency said in a statement.

In one complaint last August, a Honda driver’s lawyer told NHTSA that the car was in a crash, and both driver and passenger air bags inflated. The driver’s air bag inflator ruptured “and propelled a one-inch piece of shrapnel into the driver’s right eye.” The driver lost sight and suffered cuts requiring 100 stitches to close, the complaint said.

Takata said in a statement that it has been working closely with NHTSA for several months. The company said its engineers are trying to determine what role high levels of humidity might be playing in the malfunctions.

The company suspects that humidity is somehow degrading the combustible propellant that air bags use to rapidly inflate.

Takata’s air bags have been the subject of multiple recalls in recent months.

In April 2013, Toyota, Honda and Nissan recalled nearly 3.4 million older-model vehicles worldwide due to defective propellant in the air bags that could lead to fires.

But Takata recently realized that recall didn’t include all of the potentially faulty air bags. Earlier this month, Toyota recalled 2.27 million more cars globally. And on Monday in Japan, Honda, Mazda and Nissan together recalled nearly 3 million more.